Munin – A networked monitoring tool that displays graphs about your server(s) performance.
Nginx – A reverse proxy and web server. Very suitable for large websites.
MariaDB – A drop-in replacement for Oracle MySQL. However take note that MariaDB offers much functionality that is not present in MySQL. As such once you migrate to MariaDB, you might have a lot of hard work to revert back to MySQL.
CentMinMod – A script that eases the installation process for CentOS web servers. It has the ability to setup nginx, mysql and php + apc/memcache automatically.
OwnCloud – Set up your own privatized cloud. It enables you to sync files between different compares to a central server.
NCDU – A command line disk usage analyzer with ncurses interface. Very useful to find out largest folders or files on your server with a useful total usage overview.
PortableApps – Enables you to have a wide set of portable programs, very suitable to put on a USB and carry with you.
Ninite – Let’s you download the most popular programs without that install automatically, without any adsoftware.